The present study explores the behavioural effects of intra-accumbens injections of D-2-amino-7-phosphonoheptanoic acid (AP-7), a selective competitive N-methyl-D-aspartate (NMDA) receptor antagonist, using a swimming test procedure, in which rats were forced to swim for 6 min. The behaviour of the rats was analysed in terms of cue-directed (CDBs) and non-cue-directed behaviours (NCDBs). AP-7 (100-500 ng/0.5 microliter) dose-dependently enhanced the number of switches to CDBs, without affecting the number of switches to NCDBs. Further analysis of the data showed that the number of switches between CDBs was enhanced, while no effect was found on the number of switches from NCDBs to CDBs, from CDBs to NCDBs or between NCDBs. These data suggest that the NMDA-receptor in the nucleus accumbens is involved in the ability to switch between cue-directed behaviours.